Exploring the Interaction of Diester-Bonded Cationic Gemini Surfactant Functionalized Silver Nanoparticles with PSA: Analysis Involving Spectroscopic and Tensiometric Approaches.

Abstract

The current study describes the synthesis and characterization of AgNPs stabilized with a diester-based cationic gemini surfactant (C₁₂-E2O2-C₁₂), and their interaction behavior with protein. The main aim of the study was to explore how the surfactant-coated nanoparticle surface controls the binding and structural response of porcine serum albumin (PSA), acting here as the model protein. Synthesized C₁₂-E2O2-C₁₂-AgNPs were characterized by a spherical morphology, average size of 12.57 nm, and positive surface potential of + 19.50 ± 8.55 mV, confirming their stable dispersion. UV-Vis and fluorescence spectroscopic analyses revealed spontaneous and moderate binding of PSA to the nanoparticles, with the binding constants of 3.44 × 10⁴ M⁻¹ and 7.40 × 10⁴ M⁻¹, respectively. The interaction was mainly driven by electrostatic and hydrophobic forces, leading to changes in the secondary structure of PSA, as supported by FTIR and deconvolution of the amide I band. Surface tension studies further confirmed PSA-induced modulation of the interfacial property of the C₁₂-E2O2-C₁₂-AgNPst system, with a decrease in CMC and rise in molecular area (A_min), suggesting protein-mediated reorganization at the interface. Overall, these results offer new insights into the role of gemini surfactant-coated AgNPs in modulating protein-nanoparticles interactions relevant for biomedical and biosensing applications.